demonstrations:candle_and_rising_water

Candle and Water Rising

Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Chemical Reactions, Combustion, Heat

Alternative titles: The Rising Water

Summary

When a burning candle is covered with an inverted container standing in water, the candle eventually goes out and the water rises inside the container.

Procedure

  1. Place a lit candle upright in a shallow dish of water.
  2. Invert a glass or pitcher over the candle so its rim is submerged in the water, creating an airtight seal.
  3. Observe the flame: it burns for a short time, dims, and eventually goes out.
  4. As the flame nears extinction, note that water rises inside the container to about one-tenth of its height.

The Rising Water - Science Experiment - Hungry SciANNtist:


Why Does Water Rise? The Candle Experiment - Sally Ride Science:


📄 Candle and Rising Water Science Experiment - Frugal Fun for Boys and Girls: https://frugalfun4boys.com/candle-and-rising-water-science-experiment/
📄 Getting the facts right - Oliver Knill: https://people.math.harvard.edu/~knill/pedagogy/waterexperiment/index.html#:~:text=The%20physical%20aspect%3A%20the%20candle,decreases%20and%20the%20water%20rises.

Variations

  • Use different numbers of candles.
  • Compare results using different fuels (wax, paper, charcoal).
  • Add food coloring to the water to improve visibility.
  • Test with containers of different sizes and shapes to see how volume affects results.

Safety Precautions

  • Always perform the experiment on a stable, non-flammable surface.
  • Take care that the candle doesn't burn any plastic containers.
  • Handle candles with care—never leave them unattended.
  • Keep water nearby in case the flame spreads or wax spills.
  • Do not inhale smoke or combustion products.
  • Extinguish candles completely after the experiment.

Questions to Consider

  • Why does the water rise only after the candle goes out rather than while it burns?
  • A common misconception is that the water rises because the oxygen is being used up. Research why this is not the case.
  • How does the cooling of hot air inside the container contribute to the water rise?
  • Why is there debate about whether physics (cooling) or chemistry (oxygen depletion) is more important?